The present disclosure relates to an optoelectronic sensor arrangement, with a plurality optical transmitters positioned to transmit light into a surveillance area, and receivers to receive the light of a received cone from the surveillance area, and to a process for monitoring a surveillance area.
Known to the prior art are optoelectronic sensor arrangements having a plurality of optical transmitters that are positioned side by side on an optical transmitter strip, such that each optical transmitter emits light in a transmitted cone that irradiates a surveillance area, and having a plurality of optical receivers on an optical receiver strip which receive the light of a cone received from the surveillance area and which are designed as laterally-resolving optical receivers, such that each optical transmitter and its corresponding optical receiver form an optical receiver/transmitter pair.
Optoelectronic sensors arrangements of this kind can be used, e.g., in security equipment that monitors facilities or machines that execute dangerous movements, or that monitor automation machinery and conveyor paths.
The purpose of the optoelectronic arrangement is to determine whether an object is moving in a danger zone, so that the movement executed by equipment or machinery can be stopped, if necessary, or at least reduced in speed; or to determine whether certain objects are being transported along the conveyor paths and automation facilities in the desired fashion.
It is known to design the optoelectronic sensor arrangement both as a one-way light grid, where that the optical transmitter strip and the optical receiver strip are located on opposite sides of the surveillance area, and as a reflective light grid, such that the optical transmitter strip and the optical receiver strip are positioned in adjacent fashion on one side of the surveillance area, while a reflector is positioned opposite them in order to reflect the light emitted by optical transmitters to the optical receivers.
In both cases an object that has penetrated the surveillance area interrupts the light path between the optical transmitter and the optical receiver, so that an appropriate signal can be emitted by the optoelectronic sensor arrangement, with the result that, e.g., an alarm is triggered or machines and equipment can be stopped.
To insure the reliable functioning of the optoelectronic sensor arrangement, even when subjected to jolts or a vibrational load, the optical transmitters as a rule emit light in the form of a widening cone, while the optical receivers as a rule are able to receive light that strikes them from the cone.
An optoelectronic sensor with a plurality of optical transmitter/receiver pairs, such that the optical receivers are designed as spatially-resolving receivers, is described, e.g., by DE 197 18 390A 1. In this optoelectronic sensor the focal point of the received light is determined for each spatially-resolving receiver and is compared with a reference value. Based on the focal point of the received light and on deviations from the reference value, it is possible, e.g., to determine whether an object in the surveillance area has been reflected. However, a disadvantage here rests in the fact that as soon as different optical sources irradiate the receiver, the focal point of the received light represents only the superimposed signal of the different light sources. Under certain circumstances, reflections of objects that have penetrated the surveillance area cannot be identified, so that it is impossible to identify the object that has impermissibly entered the surveillance area.